She became a mother in 1997, naming her first child Patricia after a sister she had lost as a child.

A second daughter, Allie, was born in 1999.

And surrounded by his pretty girls, Matthew's star was rising. In 2002 he became youth minister at a Church of Christ in McMinnville, Tennessee.

“When you're in that role, you really have to walk a fine line,” Local reporter Russell Ingle. "Your kids have to look right, act right, toe the line … you know, from that perspective they looked perfect."

By then, though, Mary's family began to see less of her, the children and Matthew, who seemed, somehow, different.

Tabatha Freeman: When it was a good day and he was in a good mood, he was the best person to be around. But if at any moment, he turned, he was the very last person you wanted to be in the room with.

In February 2005, Mary gave birth to a third daughter, Brianna.

Video: Matthew Winkler's 'Stormchaser' Sermon
Just a month later, Matthew answered an exciting call. He was offered a position as lead minister at the 4th Street Church of Christ in Selmer, Tennessee, a fine old town about 80 miles east of Memphis.

Pam Killingsworth: He pulled everybody together. He was what we needed to the tee.
By late march of the following year, 2006, the family seemed to have settled quite nicely in Selmer.

Dr. Eason: He's usually here 15, 30 minutes before service, you know, shaking hands and just talking. It was very unusual for him to—to even be late.

Ten minutes became half an hour. An hour.

Finally, a delegation of church elders went to the Winkler's house to check on the young family.

Dr. Eason: A friend of mine, member of the church here—hollered at me, said he's here on the floor in the bedroom. My heart kind of fell to my stomach. And went back there and we found him.

Matthew Winkler's dead body was sprawled on the bedroom floor.

911: 911, what's your emergency?
Caller: Uh, we have an emergency. I'm not sure of the address, uh, we need the police up here right away.

Sheriff Ricky Roten raced to the scene. No windows were broken, no doors kicked in, but in the bedroom, on the floor, police found Matthew's body and a terrifying mystery: where was Mary? Where were the girls? Had someone kidnapped his family?

Sheriff: Probably. And you always think about the safety of the kids. The first thing, where in the world were the kids at? That's one of the things that probably hit me too. There's three kids here. Where in the world are they at? How do you do this?

Sheriff: None of the kids rooms were torn up. Nothing was thrown. Everything was just in its normal place. Everything was just normal and then the kids were gone.

An immediate Amber Alert went out and the search was on for the victims.

At the crime scene, the details were shocking. Matthew had a massive wound in his back.

Sheriff: It wasn't a question what happened to him, it was just who done it. Have any idea why?

He'd been shot with a 12 guage shotgun at point blank range, apparently while he was sleeping. The phone was unplugged. Officers faced the chilling possibility that he'd been left -- unable to call for help -- to die.

As police circulated pictures of Mary and her girls all around the country, a dreadful feeling, close to panic, ensued.

Sheriff: Maybe somebody had moved it to keep him or somebody from dialing 911 for help.
Tabatha Freeman: I knew that something tragic had happened.
Clark Freeland: I kept calling her cell phone, "Call home, Carol. Wherever you are, call home and talk to daddy.you must do that."

But the longer police studied the crime scene and the longer they looked for Mary -- the more they wondered if maybe she wasn't a victim. Maybe she was a suspect.

Then, an alert officer in Alabama spotted the Winkler van.

Whitlock: At that time, we did a felony traffic stop.

The petite preacher's wife seemed strangely calm.

Whitlock: It was almost like she was expecting it. She immediately got out of the car, looked at us, didn't say a word, didn't appear to be stressed or anything. It was just a blank look on her face.

Police suspicions grew when they found a 12-gauge shotgun in the back of the van. Mary was marched backwards, hands on her head, handcuffed and read her rights. Her daughters, 8-year-old Patricia, 6 year old Allie, and the baby, Breanna, were turned over to child services.

They took Mary to the police station, where they handcuffed her to a bench.

When Tennessee Bureau of Investigation agent Stan Stabler came to get her a few hours later for questioning, he was struck by her cool demeanor.

Stan Stabler: She didn't appear to be emotionally upset or—or traumatized by what had happened. The fact that she was so calm and collected.

Stabler questioned Mary for over an hour, and the interrogation was captured on audio tape.

Stabler: There's really only one person really knows what happened. And that's you.

The next day, sitting there in her jail cell, at the center of the whole country's horrified attention, she had an unexpected visitor.

It was a lawyer named Steve Farese.

Steve Farese: I saw Mary as the consummate underdog.

Farese is a famous son of Ashland, Mississippi -- population 395 -- where a firm started by his father anchors the town square.

Steve Farese: I told her who I was—what I intended to do for her. And—that I'd be back to see her on Monday. And then I call Leslie.

Leslie Ballin is a prominent Memphis attorney and together the two had defended murderers and thugs for years.

Leslie Ballin: He asked me, "Do you want to go to Selmer?" and so I said, "All right. How much retainer fee?" Because we do this generally for profit, for money.
Keith Morrison: Really?
Leslie Ballin: Yeah. And he says something about pro bono. And I said, "Steve, hold on, there's something the matter with my cell phone. I could have sworn you said 'pro bono.'" And I said, "Are you crazy, why?" And he said because it's the right thing to do.

In other words, Farese had committed them both to work for free, even though it appeared an almost hopeless task. Even as she entered her not guilty plea, the evidence piled up and she was potentially facing the death penalty.

Farese: She had nothing going for her. Kids had been ripped away. She was thrown in jail. She had confessed. There was no way out. That's my kind of person.

District Attorney Michael Dunavant led the prosecution. At 36, he was the youngest D.A. in state history, elected just months before the trial.

Keith Morrison: Boy, to get elected and have that thing staring you in the face must be daunting I would think?
Mike Dunavant: Well, it was.

Dunavant chose his most experienced and unflappable assistant district attorney, Walt Freeland, to prosecute the preacher's wife. Together they assembled a powerful case.

Mike Dunavant: I wouldn't say slam dunk, but I would say that we felt confident that we had evidence to prove premeditated first-degree murder.

It was a year after that dreadful morning in Selmer when Mary Winkler's trial finally began for first-degree murder.

The facts seemed stark and plain. As Matthew Winkler lay sleeping, his devoted wife, the paragon of Christian virtue, shot him in the back with a shotgun. And as the life drained out of his body, she put the kids in the van and simply drove away.

Walt Freeland: The state will show you ample evidence that Mary Winkler premeditatedly, unlawfully, and intentionally, killed Matthew Winkler, a man that did not deserve to die.

Video: State: Winkler murder "was no accident"
The prosecution would need to convince the jury of premeditation -- that Mary had planned out and executed this murder in a calculated way. And who best to lead off the prosecution case than Matthew's own father, a renowned minister of the Church of Christ.

Walt Freeland: And what was your father's occupation?
Dan Winkler: The very same.
Walt Freeland: And what was his father's occupation?
Dan Winkler: The very same.
Freeland: So Matthew was a fourth-generation preacher, is that right?
Winkler: That is correct, yes sir.

Matthew's father said he'd raised his son to be considerate and kind.

Dan Winkler: We told all three of our sons, who did well in football to exercise their force on the field, but be gentle off the field and be nothing but a gentleman off the field.

Then a police officer told about discovering a telephone at Matthew's feet.

Freeland: Was there anything unusual about the telephone that you observed?
Roger Rickman: There was no phone line plugged into it.

The unplugged phone was evidence, said the prosecution, of Mary's premeditated effort to ensure that Matthew had no way to call for help.

A firearms expert testified that the shotgun found in Mary's van was indeed the murder weapon, and that it worked just fine.

Steve Scott: I found no dysfunction in the firearm itself that would indicate that it would fire other than by pulling the trigger.

And then, of course, there was the so-called confession tape -- the most damaging evidence of all. The prosecution played all one hour and five minutes of it, emphasizing all the lines that suggested premeditation.

Interview tape
Mary Winkler: I always thought it was going to kick hard. There was a little bang, it wasn't near what I thought.

What satanic impulse had gripped the saintly heart of Mary Winkler?

It's an old town, Selmer, Tennessee, with a population not quite 5,000 souls.

A Bible Belt town, its spires reach up for heaven and ask: What could possibly prompt a preacher's wife to murder her own husband?

Keith Morrison: You look into those soft, sweet eyes and what do you see?
Mike Dunavant: I see a cold-blooded killer who didn't want to be married to a Church of Christ preacher anymore, and murder became more attractive than divorce.

To the prosecutor, the facts seemed pretty clear. Matthew was asleep and Mary shot him. But why?

A prosecutor needs motive, and sure enough, a little investigating revealed a sad story as old as human commerce.

Mary had become involved in some illegal bank schemes, said the prosecutor. She had gotten them into trouble and Matthew was just about to find out.

In fact, in the months leading up to Matthew's death, the Winkler finances had become something of a shambles.

It began in December 2005, said the prosecution, when -- quite out of the blue -- a check for nearly $6,500 arrived at the already cash-strapped Winkler home.

Walt Freeland: Was there any significance to you a-- about what happened four days after that?
Brent Booth: Yes.
Walt Freeland: And what is that?
Brent Booth: Opening a bank account in an out-of-town bank, First State Bank in Henderson, Tennessee.

By late February Mary had five bank accounts. Prosecutors argued that she would deposit a worthless check into one bank, then draw money on the check and put it into another bank before the 1st bank discovered it was worthless. It's called check kiting, it's illegal, and bank tellers noticed.

Judi Mills: This check came back to us -- stamped "fraudulent item."

Amy Hollingsworth: In February, there was a check deposited in the amount of $7,000 that I had to put a hold on.

There were others, too, all signed by Mary.

Walt Freeland: Were any of these checks signed by Matthew Winkler?
Amber Brown: No.

By March 20, just two days before Matthew's death, Mary was scrambling. She made 16 telephone transfers, account to account, in a 30-hour period.

By the next day, March 21, pressure on Mary seemed to be building. That day, she worked as a substitute teacher. A fellow teacher said she walked past Mary's classroom several times, and each time, Mary was on the phone.

Kacey Michelle Broadway: She was pacing back and forth. And she just had a upset look in her-- on her face.

Well of course she was upset, said the prosecutor. Those phone calls were from bankers ordering her to come a meeting -- and to bring her husband.

Amy Hollingsworth: I did say to her that if -- if we couldn't work out -- if she wasn't able to come in, it would be turned over to our security department.

Walt Freeland: Was a deadline or a date discussed with her as to when these needed to be resolved?
Amy Hollingsworth: Yes, sir.

That date was March 22.

March 22 was the day Matthew died and she was going to have to explain herself.

Keith Morrison: With him there.
Mike Dunavant: That's right. He's the Church of Christ preacher. To explain that his wife has been doing financial crime, that she is frauding the local banks … we felt like that was as good a motive as any to show that she was duplicitous, she was thoughtful, she was astute, she was cold and calculating.

And so the prosecution rested, saying it all added up to first-degree murder. Or did it?

"Mary Winkler had what appeared to everyone," defense attorney Steve Farese said in his opening statement, "to have had a marriage made in heaven. But behind closed doors -- it was a living hell."

Defense attorney Steve Farese was about to offer an entirely different answer to the question "Why did Mary Winkler kill her husband?"

The answer, said Farese, started with a man who was not what he seemed to be.

Farese: Matthew Winkler was the face of that family. He was the important one. He was the charismatic one … And he was the mean one. Mary was his whipping boy.

Farese laid out a harrowing scenario, claiming Mary had suffered in silence through years of physical, mental and sexual abuse at the hands of her husband.

The defense dismissed the notion that the unplugged phone was incriminating, showing the jury a police photo taken in Mary's hotel room in Alabama and suggesting she may have unplugged both phones for the baby to play with.

Leslie Ballin: It's not connected.
Travis Long, Jr: It appears not to be connected to anything, yes sir.
Leslie Ballin: And it'd be down where a one year old could play with it, wouldn't it?
Travis Long, Jr: It's on the floor where anyone could get to it.

And what about that taped interrogation? Hadn't Mary already confessed?

Steve Farese: No matter which way she answers it -- she's got to say she shot him, would you agree?
Stan Stabler: No, sir, I don't.

Steve Farese: Did Mary winker ever tell you she shot her husband, yes or no?
Stan Stabler: She did not speak those words. No, sir.

Finally, the defense turned to the shotgun, which was a key element of their case.

The action called racking the gun is required to move the shotgun shell into the chamber. The defense argued the noise it makes would have awakened Matthew, so the gun must have been loaded and primed before Mary ever picked it up.

Steve Farese: It makes a distinctive sound, does it not?
Agent Stan Stabler: Yes, sir, it does.
Steve Farese: Lights could be off, it could be dark and you hear that, you know what it is?
Agent Stan Stabler: Yes, sir, I do.

And if the rifle was already loaded and cocked, could Mary have accidentally pulled the trigger?

Reluctantly the state's own gun expert acknowledged it could happen.

Steve Farese: So is it possible for someone to unintentionally discharge a firearm?
Steve Scott: I suppose it would be. Yes, sir.
Steve Farese: Okay. Now, not only is it possible, it's been documented. Would you agree?
Steve Scott: I have acci-- unintentionally discharged a firearm before.

But even if Mary didn't intend to pull the trigger, and that was only an 'if' -- why in heaven's name was she pointing a loaded shotgun at a sleeping Matthew?

To answer that question, the defense would have to undermine Matthew's stellar Church of Christ persona. Was he in fact the good, kindly, moral, force for God that he appeared to be? Or was something venal and cruel hidden behind that holy facade?

The defense produced a series of witnesses claiming Matthew was not all he appeared, starting with Mary's sister.

Tabatha Freeman: He pretty much dictated anything that she did. She wasn't allowed to make any decisions for herself.

She said as time went on, he isolated Mary from her family.

Tabatha Freeman: A very bubbly out-going sister became very subdued. And I didn't get to see her.

And this highway patrolman said Matthew yelled at his family about a barking dog.

Sergeant Jimmy Jones: He began to shout and raise his arms and -- and basically out of control.
Steve Farese: Let me ask you this. What was he acting like to you that day?
Sergeant Jimmy Jones: A bully. I nicknamed him the Tasmanian devil."

One Sunday morning, a church member noticed Mary had a black eye, and he saw something else he didn't like at a church supper.

Rudy Thomsen: Mary was just bubbling, just … just talking to everybody and grinning and cutting up and just having a big time. And then Matthew walked in, and it was like you had taken a switch and flipped it. And her head went down. Her hands came together. She walked around. Totally different than she had been just a second before.

The defense claimed not only was Matthew cruel and abusive, but Mary was especially defenseless -- because she'd already been living with a secret debilitating trauma going back to her early childhood.

Forensic psychologist Lynn Zager said Mary's troubles began when she was 13, when her little sister Patricia suddenly died and Mary's own deeply religious family steered her away from a school counselor's aid.

Dr. Lynne Zager: I believe that that was the start of significant mental health issues for Mary.

The untreated mental illness was so severe, said the doctor, that as a teen, Mary developed post-traumatic stress disorder (PTSD).

Over the course of many conversations, Zager said Mary revealed ugly secrets about her marriage.

Zager testified she believed PTSD made Mary especially vulnerable to the abuse, and in times of crisis, to what she called dissociative episodes -- moments where Mary might lose her ability to think or plan.

Dr. Lynne Zager: They sort of step outside themselves and they go into an episode. Sort of like being in a fog -- might be a good way of describing it.

The doctor said something happened the morning of March 22, 2006, something so horrific it caused Mary to lose herself, to "go into a fog."

Leslie Ballin: Was she capable of forming the intent to specifically commit any crime at the time in question?
Dr. Lynne Zager: I don't believe so. No.

A respected minister with a mean streak was with a loyal wife on the edge. But how did that end in death? Only Mary knew.

Steve Farese: Unless lightning struck, she was going to have to testify.

And so Mary Winkler took the stand.

Steve Farese: May it please the court, the defense calls the defendant, Mary Carol Winkler.

She began with that other central event in her life: the death of her sister, Patricia.

Mary Winkler: We were just the best of friends and we never got into one fight. She was mine and mom and daddy's biggest cheerleader.

Mary said she and her brothers and sisters grew up in the Church of Christ, and they were all used to firm orders from the head of the household.

Steve Farese: Who made all the decisions of that household?
Mary Winkler: Daddy.

Mary told the jury that in her marriage, abuse started within a few months.

Steve Farese: Tell the jury how he had been physical with you. Mary.
Mary Winkler: Pushed me down. Used his belt. Kick.

Mary testified Matthew spanked the children, and occasionally it got out of hand. She said his actions when Allie was a baby were particularly upsetting.

Mary Winkler: If she was crying and she -- it was time to go to bed. And he would suffocate her to get her -- go-- get quiet and go to sleep.
Steve Farese: What do you mean by suffocate her?
Mary Winkler: He'd pinch her nose and hold her mouth.
Steve Farese: And would -- would you let him do that to your child?
Mary Winkler: I just couldn't stop him.

She told jurors she hid the abuse from everybody because she was ashamed.

Steve Farese: Mary, would you open that sack please?

But no one was prepared for this.

Steve Farese: What's in that sack, Mary?
Mary Winkler: A shoe and a wig.
Steve Farese: Show me the shoe that's in there. Put it up on the side there. Is that the kind of shoe that you'd wear to church?
Mary Winkler: No, sir.
Steve Farese: What else is in the sack Mary?
Mary Winkler: Wig.

It was a preacher's secret: hundreds of Web pages of porn. Mary testified Matthew forced her to look at porn and then forced her to have oral and anal sex.

Steve Farese: Was it supposed to be like the movies or the picture?
Mary Winkler: Probably.

After work on March 21, the night before Matthew died, Mary said the family ate pizza and the girls watched "Chicken Little" and then went to bed. Matthew put on a movie, and Mary went to sleep.

Steve Farese: Did you have any relations that night?
Mary Winkler: Yes, sir.
Steve Farese: Were they ordinary, normal?
Mary Winkler: Ordinary for us.

Mary told the jury that around 6 a.m. the following morning, the baby cried and Matthew kicked her out of bed.

Steve Farese: What do you mean kicked you out of the bed?
Mary Winkler: He just caught me somewhere in the low of my back and I was on the floor.
Steve Farese: With his foot?
Mary Winkler: Yes, sir.

What came next, according to the defense, is the event that just might have triggered that "fog" the forensic psychologist testified about.

Mary said she followed Matthew to the nursery, where she found him blocking the baby's airways as he had done with Allie years before.

She testified that she asked for the baby.

Mary Winkler: He just threw his arms up and walked out and walked away from the crib … and as he walked out of the door he just slammed the door frame.
Steve Farese: With what?
Mary Winkler: His open-- his open hand.

Steve Farese: What did you want to talk to him about?
Mary Winkler: I just wanted him to stop being so mean.

And that's where Mary's memory of what happened up there at the little parsonage gets, well, vague. Somehow, and she isn't quite sure how, she wound up standing at the foot of the bed, holding Matthew's shotgun.

Walt Freeland: You remember the part about Matthew suffocating Breanna, and you remember the part about your going to make coffee.
Mary Winkler: Okay.
Walt Freeland: You just don't know how that gun came to shoot Matthew in the middle of the back. That's the part you don't remember.
Mary Winkler: Yes, sir.

It was a day of devastating testimony for Matthew's family and for Mary's family -– and clearly draining for Mary herself.

Now the case would go to the jury, which was composed of 10 women and two men.

Then, in the jury room, finally able to speak, they found themselves sharply divided.

Bill Berry: I was pulling for-- for her to be-- at least second-degree murder.

Amy Mullins: I felt that she was not guilty.

Six jurors sat down with Dateline -- a customer service rep, a teacher's assistant, a computer drafter, a retired machinist and preacher, a paper mill worker, and this mother and student.

They said they didn't take an initial vote.

Jennifer McKee: We all kind of just blurted out whatever we thought. You know?

Angie McMahan: If somebody said something that another person didn't like they-- would interject. It was just kind of like a big argument.

The jury had been instructed to consider five different charges against Mary -- all the way from premeditated first-degree murder with life in prison, down to criminally negligent homicide, almost an accident, which would mean as little as a year behind bars.

What the jury didn't know was that if they convicted Mary of first- or second-degree murder, she would permanently lose any parental rights to her three girls.

Inside the jury room debate dragged on. The jurors examined that high-heeled shoe and the wig, and every one of them handled and racked the shotgun. To many, the process was agonizing.

Bill Berry: I couldn't eat. I was sick … knowing we were having to -- determine whether this girl went to prison or not.

With the national press corps standing by, at 5:30 p.m., after seven hours of deliberations, there was a verdict.

Judge McCraw: Ms. Winkler, if you could please stand ma'am? Alright, ma'am, the verdict reads as follows: we the jury find the defendant, Mary C. Winkler, guilty of voluntary manslaughter.

It meant she would spend no more than six years in prison and could eventually regain custody of her girls.

Leslie Ballin: Immediately upon the verdict being read, she wanted to know, "Does this mean that I can get my children back?"
Keith Morrison: Just right then?
Ballin and Farese (in unison): Right then.

Jurors told us they couldn't agree on whether the gun could go off accidentally, but were deeply affected by a preacher's alleged sexual coercion and by the testimony of the psychologist.

Angie McMahan: She gave us the reasonable doubt.

About Mary's credibility, jurors disagreed.

Bill Berry: We were supposed to believe everything that Mary said, but there's a few things that I didn't believe.

Amy Mullins: I believed every word that came out of her mouth. And I believe that she still has more that she hasn't said.

After time served and other considerations, Mary will spend just 67 days in custody, most of them in a psychiatric facility, followed by probabation. It was a victory for the defense.

Steve Farese: This has been a hard-fought case. At the end of the day, there has been a death and that cannot be ignored.

The prosecution took some comfort too.

Michael Dunavant: Let's not forget that the jury did convict her of the class C felony of homicide. An intentional and knowing killing.

Matthew's father stood before the press and did his best to defend his son's memory.

Dan Winkler: We're very grateful for the privilege and honor that was ours to be the parents of Matthew Brian Winkler.

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.